A number of fluoro-sulfur compounds have beneficial applications. For example, sulfur tetrafluoride (SF4) is a widely-used compound produced yearly at the metric ton level, which can be utilized as a deoxofluorinating reagent in converting carboxylic acids, aldehydes, some alcohols and ketones into their corresponding deoxofluorine derivatives (i.e. R—CF3, R—CHF2, RF, RR′—CF2). SF4 is also utilized as an etching agent in the electronics industry. Moreover, SF4 can be utilized as a precursor for the synthesis of other important fluorinated products such as, without limitation, pentafluorosulfur chloride (SF5Cl), pentafluorosulfur bromide (SF5Br), and sulfur hexafluoride (SF6).
Sulfur hexafluoride (SF6), is a compound that is produced by the thousands of metric tons each year, and its worldwide uses include: acting as a PCB replacement and an inert dielectric medium for electrical equipment, the etching of semiconductors, the casting of magnesium, the manufacture of thermal windows, a source of thrust in some rocket propulsion systems, the tracing of air flow through industrial systems, a tamponade for retinal holes of the eye and in medical imaging.
Compounds harboring fluoro-organic modifications such as R—CF3, R—CHF2, RF, RR′—CF2 and RSF5, have been used in a variety of applications including fluorinated therapeutic and diagnostic drugs, pesticides, herbicides, antibiotics, perfluorinated blood substitutes, fungicides, polymer solvents, polymers, lubricants, liquid crystals, surface-active agents, high-boiling solvents, stable solvents, electrically conducting polymers and the like. Utilizing an SF5 group in the place of CF3 offers many advantages. Particularly, the SF5 group possesses greater electronegativity than CF3. Moreover, compounds containing SF5 may be further distinguished by their outstanding chemical properties including high to extreme chemical and thermal stability, hydro- and oleophobicity, lipophilicity, high-density, reduction of shock sensitivity in explosives, low boiling point, low polarizability and low surface tension.
While SF5-derivatives offer these advantages, they have been difficult to synthesize. The difficulty of obtaining such compounds is in part related to the difficulty of obtaining sufficient and affordable quantities of SF5Cl or SF5Br, which are the principal chemical reagents used to synthesize and obtain a number of organic or inorganic derivatives that bear the SF5-radical moiety. SF5Cl, particularly, is a valuable reactant to produce SF5-radical bearing derivatives of (sulfur hexafluoride) SF6 and may be reduced to disulfur decafluoride (S2F10) with the latter being converted into pentafluorosulfur bromide (SF5Br). SF5Cl can also be used in the synthesis of SF6. It is of interest that SF5Cl can be particularly used in the manufacture of SF6 by a pyrogenic route (e.g. U.S. Pat. No. 4,390,511), whereby a disproportionation occurs according to the following reaction:SF5Cl→½SF6+½SF4+½Cl2 In this method, SF6 is obtained that is free of S2F10, a compound believed to be highly toxic and a by-product of the manufacture of SF6 by the reaction of sulfur with fluorine. Accordingly, the use of SF5Cl can be used to produce high purity SF6.
Collectively, a variety of methods have been demonstrated as processes for the production of SF6 and include U.S. Pat. Nos. 2,883,267, 2,912,307, 3,054,661, 3,345,277, 3,399,036, 3,373,000, 4,390,511, 5,639,435 and Japanese Patent No. 7,625,497. These methods frequently employ electrochemical preparation, high reaction temperatures and pressures, and/or utilize highly-reactive and/or costly reactants that can include F2, SF5Cl, IF5, SF4, ClF and HF.
SF5Br is also a valuable chemical compound that has been demonstrated as a reactant for the efficient production of SF5-radical bearing chemicals; also known as derivatives of SF6.
Currently available methods of producing fluoro-sulfur compounds suffer a number of drawbacks. The drawbacks generally include the use of excessive temperatures, electrochemical preparation, expensive and/or hazardous reactants, the requirement for numerous successive steps or long reaction times, the production of low or variable yields and/or the generation of toxic by-products. Accordingly, there is room for improvement in the synthesis of fluoro-sulfur compounds.